Test results and applications of an AUV-borne controlled source electromagnetic (CSEM) system

摘要

Towed controlled source electromagnetic systems (CSEM) are used to map subsurface resistivity structure. In 2014 and 2015, Fukada Salvage and Marine Works Co. Ltd and Ocean Floor Geophysics used a towed CSEM system developed by the Scripps Institution of Oceanography to map gas hydrate deposits. Towing the system at a constant depth in terrain with steep bathymetric gradients, such as in the vicinity of hydrothermal chimneys associated with seafloor massive sulfide (SMS) deposits, would prove difficult. Mounting electrodes on an AUV with a seafloor mounted transmitter as a source could overcome this difficulty, with the added benefit of simultaneous bathymetric mapping with a multibeam. To test the possibility of mounting electrodes on an AUV for CSEM mapping, a set of experiments were run to measure the noise levels of electric field measurements made using an AUV. The results of these tests are presented here.